Remission refers to a stage of lesser intensity, when something subsides or improves. Remission is usually a good thing — like when your cancer is in remission, it means that it is manageable and not getting any worse.
Remission comes from the Latin remissionem, meaning "relaxation; a sending back." If something difficult lets up, you'll be able to relax a little. For example, if you are being pelted non-stop during a dodgeball game, you'd hope for a remission so you'd have a minute to take a breath and find your glasses. Another meaning of the noun remission is a payment. Your college tuition remission must be taken care of before you start classes.